PROTEOMICS CORE SUMMARY/ABSTRACT A comprehensive molecular understanding of T cell receptor proximal signaling and the biochemical networks regulated by Ras exchange factors in peripheral T cell signaling requires both a global analysis of phosphorylation events and protein interactions across the entire proteome of a cell as they occur in either the basal or stimulated T cell state. The proteomic core will make these cutting-edge, quantitative capabilities available to the investigators of this proposal. The Proteomics Core will provide essential expertise for the timely analysis of the protein composition and post-translational modifications for both projects described in this proposal. The proteomic core will provide identification and relative quantitation of the protein composition and post-translational modification state of proteins using cutting-edge LC/MS techniques using a recently acquired Q Exactive mass spectrometer. Dr. Arthur Salomon, who has been using LC/MS technology to study TCR signaling pathways for more than a decade, brings his expertise to the Program and serves as Proteomics Core facility Director. The core will identify tyrosine as well as serine threonine phosphorylation sites from SILAC and label-free samples from T cell lines, primary mouse T cells, and in vitro kinase reactions from Project #1 (Weiss, PI) and protein-protein interactors from Project #2 (Roose PI). It will also perform statistical evaluation and interpretation of phosphorylation sites from cell studies.